Organic electroluminescent materials and devices

ABSTRACT

A luminescent materials including donor-acceptor compounds with a nitrogen containing donor connected to the 1-position of a carbazole and triazene acceptor connected at the 9-position is disclosed.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to organic light emitting devices. Morespecifically, the present disclosure pertains to luminescent materialscomprising donor-acceptor compounds with a nitrogen containing donorconnected to the 1-position of a carbazole and triazene as the acceptorfor use as emitters in organic light emitting diodes.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled inthe art, a first work function is “greater than” or “higher than” asecond work function if the first work function has a higher absolutevalue. Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

SUMMARY OF THE INVENTION

According to an embodiment of the present disclosure, a compound havinga structure according to the following Formula 1 is disclosed:

In Formula 1, R^(a) to R^(g), R¹ and R² are independently selected fromthe group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof. Ar¹ to Ar³ areindependently substituted or unsubstituted aryl or heteroaryl and canconnect to one another to form fused ring(s). L is a direct bond or alinker.

According to another embodiment, a first device comprising a firstorganic light emitting device is disclosed. The first organic lightemitting device comprising: an anode; a cathode; and an emissive layer,disposed between the anode and the cathode, wherein the emissive layercomprises a first emitting compound having a structure according toFormula 1:

In Formula 1, R^(a) to R^(g), R¹ and R² are independently selected fromthe group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof. Ar¹ to Ar³ areindependently substituted or unsubstituted aryl or heteroaryl and canconnect to one another to form fused ring(s). L is a direct bond or alinker.

According to yet another embodiment, a formulation comprising a compoundhaving a structure according to Formula 1 is also disclosed.

The compound of the present disclosure can be used in OLEDs as emitters,hosts, charge transport materials, in both single color or multiplecolor devices. The compound can be easily utilized in fabrication ofOLEDs because the compound can be vapor-evaporated or solutionprocessed. The compound is useful as emitters because it provides highefficiency OLEDs without using organometallic compounds.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device that can incorporate theinventive host material disclosed herein.

FIG. 2 shows an inverted organic light emitting device that canincorporate the inventive host material disclosed herein.

FIG. 3 shows Formula 1 as disclosed herein.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-1”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporatedby reference.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which areincorporated by reference.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of host materials are disclosed inU.S. Pat. No. 6,303,238 to Thompson et al., which is incorporated byreference in its entirety. An example of an n-doped electron transportlayer is BPhen doped with Li at a molar ratio of 1:1, as disclosed inU.S. Patent Application Publication No. 2003/0230980, which isincorporated by reference in its entirety. U.S. Pat. Nos. 5,703,436 and5,707,745, which are incorporated by reference in their entireties,disclose examples of cathodes including compound cathodes having a thinlayer of metal such as Mg:Ag with an overlying transparent,electrically-conductive, sputter-deposited ITO layer. The theory and useof blocking layers is described in more detail in U.S. Pat. No.6,097,147 and U.S. Patent Application Publication No. 2003/0230980,which are incorporated by reference in their entireties. Examples ofinjection layers are provided in U.S. Patent Application Publication No.2004/0174116, which is incorporated by reference in its entirety. Adescription of protective layers may be found in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al., which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink-jet and OVJD. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processibility than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention maybe incorporated into a wide variety of consumer products, including flatpanel displays, computer monitors, medical monitors, televisions,billboards, lights for interior or exterior illumination and/orsignaling, heads up displays, fully transparent displays, flexibledisplays, laser printers, telephones, cell phones, personal digitalassistants (PDAs), laptop computers, digital cameras, camcorders,viewfinders, micro-displays, 3-D displays, vehicles, a large area wall,theater or stadium screen, or a sign. Various control mechanisms may beused to control devices fabricated in accordance with the presentinvention, including passive matrix and active matrix. Many of thedevices are intended for use in a temperature range comfortable tohumans, such as 18 degrees C. to 30 degrees C., and more preferably atroom temperature (20-25 degrees C), but could be used outside thistemperature range, for example, from −40 degree C to +80 degree C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The term “halo” or “halogen” as used herein includes fluorine, chlorine,bromine, and iodine.

The term “alkyl” as used herein contemplates both straight and branchedchain alkyl radicals. Preferred alkyl groups are those containing fromone to fifteen carbon atoms and includes methyl, ethyl, propyl,isopropyl, butyl, isobutyl, tert-butyl, and the like. Additionally, thealkyl group may be optionally substituted.

The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals.Preferred cycloalkyl groups are those containing 3 to 7 carbon atoms andincludes cyclopropyl, cyclopentyl, cyclohexyl, and the like.Additionally, the cycloalkyl group may be optionally substituted.

The term “alkenyl” as used herein contemplates both straight andbranched chain alkene radicals. Preferred alkenyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkenyl groupmay be optionally substituted.

The term “alkynyl” as used herein contemplates both straight andbranched chain alkyne radicals. Preferred alkyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkynyl groupmay be optionally substituted.

The terms “aralkyl” or “arylalkyl” as used herein are usedinterchangeably and contemplate an alkyl group that has as a substituentan aromatic group. Additionally, the aralkyl group may be optionallysubstituted.

The term “heterocyclic group” as used herein contemplates aromatic andnon-aromatic cyclic radicals. Hetero-aromatic cyclic radicals also referto heteroaryl. Preferred hetero-non-aromatic cyclic groups are thosecontaining 3 or 7 ring atoms which includes at least one hetero atom,and includes cyclic amines such as morpholino, piperdino, pyrrolidino,and the like, and cyclic ethers, such as tetrahydrofuran,tetrahydropyran, and the like. Additionally, the heterocyclic group maybe optionally substituted.

The term “aryl” or “aromatic group” as used herein contemplatessingle-ring groups and polycyclic ring systems. The polycyclic rings mayhave two or more rings in which two carbons are common to two adjoiningrings (the rings are “fused”) wherein at least one of the rings isaromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl,heterocycles, and/or heteroaryls. Additionally, the aryl group may beoptionally substituted.

The term “heteroaryl” as used herein contemplates single-ringhetero-aromatic groups that may include from one to three heteroatoms,for example, pyrrole, furan, thiophene, imidazole, oxazole, thiazole,triazole, pyrazole, pyridine, pyrazine and pyrimidine, and the like. Theterm heteroaryl also includes polycyclic hetero-aromatic systems havingtwo or more rings in which two atoms are common to two adjoining rings(the rings are “fused”) wherein at least one of the rings is aheteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls,aryl, heterocycles, and/or heteroaryls. Additionally, the heteroarylgroup may be optionally substituted.

The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group,aryl, and heteroaryl may be optionally substituted with one or moresubstituents selected from the group consisting of hydrogen, deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

As used herein, “substituted” indicates that a substituent other than His bonded to the relevant position, such as carbon. Thus, for example,where R¹ is mono-substituted, then one R¹ must be other than H.Similarly, where R¹ is di-substituted, then two of R¹ must be other thanH. Similarly, where R¹ is unsubstituted, R¹ is hydrogen for allavailable positions.

The “aza” designation in the fragments described herein, i.e.aza-dibenzofuran, aza-dibenzonethiophene, etc. means that one or more ofthe C—H groups in the respective fragment can be replaced by a nitrogenatom, for example, and without any limitation, azatriphenyleneencompasses both dibenzo[f,h]quinoxaline and dibenzo[f,h]quinoline. Oneof ordinary skill in the art can readily envision other nitrogen analogsof the aza-derivatives described above, and all such analogs areintended to be encompassed by the terms as set forth herein.

It is to be understood that when a molecular fragment is described asbeing a substituent or otherwise attached to another moiety, its namemay be written as if it were a fragment (e.g. naphthyl, dibenzofuryl) oras if it were the whole molecule (e.g. naphthalene, dibenzofuran). Asused herein, these different ways of designating a substituent orattached fragment are considered to be equivalent.

As used herein, the phrase “electron acceptor” or “acceptor” means afragment that can accept electron density from an aromatic system, andthe phrase “electron donor” or “donor” means a fragment that donateselectron density into an aromatic system.

It is believed that the internal quantum efficiency (IQE) of fluorescentOLEDs can exceed the 25% spin statistics limit through delayedfluorescence. As used herein, there are two types of delayedfluorescence, i.e. P-type delayed fluorescence and E-type delayedfluorescence. P-type delayed fluorescence is generated fromtriplet-triplet annihilation (TTA).

On the other hand, E-type delayed fluorescence does not rely on thecollision of two triplets, but rather on the thermal population betweenthe triplet states and the singlet excited states. Compounds that arecapable of generating E-type delayed fluorescence are required to havevery small singlet-triplet gaps. Thermal energy can activate thetransition from the triplet state back to the singlet state. This typeof delayed fluorescence is also known as thermally activated delayedfluorescence (TADF). A distinctive feature of TADF is that the delayedcomponent increases as temperature rises due to the increased thermalenergy. If the reverse intersystem crossing rate is fast enough tominimize the non-radiative decay from the triplet state, the fraction ofback populated singlet excited states can potentially reach 75%. Thetotal singlet fraction can be 100%, far exceeding the spin statisticslimit for electrically generated excitons.

E-type delayed fluorescence characteristics can be found in an exciplexsystem or in a single compound. Without being bound by theory, it isbelieved that E-type delayed fluorescence requires the luminescentmaterial to have a small singlet-triplet energy gap (ΔE_(S-T)). Organic,non-metal containing, donor-acceptor luminescent materials may be ableto achieve this. The emission in these materials is often characterizedas a donor-acceptor charge-transfer (CT) type emission. The spatialseparation of the HOMO and LUMO in these donor-acceptor type compoundsoften results in small ΔE_(S-T). These states may involve CT states.Often, donor-acceptor luminescent materials are constructed byconnecting an electron donor moiety such as amino- orcarbazole-derivatives and an electron acceptor moiety such asN-containing six-membered aromatic rings.

The present disclosure provides compounds with multiple-nitrogen donorsand triazine acceptors which may show strong CT emission. The inventorsdiscovered that donor-acceptor compounds with a nitrogen containingdonor connected to the 1-position of a carbazole and triazene acceptorconnected at the 9-position may be more efficient emitters with emissionoriginated from the charge transfer (CT) state. Substitution at the 1position of the carbazole causes a significant steric hindrance betweenthe substitutents at the 1 position and the 9-position. This sterichindrance was expected to result in a disruption of the through-bondconjugation of the donor and the acceptor. Unexpectedly, however, thedonor-acceptor compounds exhibited efficient emission. This appears tobe the result of a through-space interaction between the donor and theacceptor enabled by the donor and acceptor being adjacent to each other.This may be an effective mechanism of charge transfer emission withoutlowering the emission energy due to through-bond π-conjugation. Theemission can be tuned by varying the strength of the donor-acceptorinteraction and the resulting energy of the CT state. The compounds maybe used as emitters in OLED.

According to an embodiment, the donor-acceptor compound with a nitrogencontaining donor connected to the 1-position of a carbazole and triazeneas the acceptor has a structure according to Formula 1:

wherein R^(a) to R^(g), R¹ and R² are independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and wherein Ar¹ to Ar³are independently substituted or unsubstituted aryl or heteroaryl andcan connect to one another to form fused ring(s) and, wherein L is adirect bond or a linker.

According to one embodiment, the alkyl and cycloalkyl in Formula 1 canbe selected from the group consisting of methyl, ethyl, propyl,1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl, pentyl,1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl,1,2-dimethylpropyl, 2,2-dimethylpropyl, cyclopentyl, cyclohexyl,partially or fully deuterated variants thereof, and combinationsthereof. The aryl and heteroaryl in Formula 1 can be selected from thegroup consisting of phenyl, biphenyl, terphenyl, tetraphenyl,pentaphenyl, pyridine, phenyl pyridine, pyridyl phenyl, triphenylene,carbazole, fluorene, dibenzofuran, dibenzothiophene, dibenzoselenophene,aza-triphenylene, aza-carbazole, aza-fluorene, aza-dibenzofuran,aza-dibenzothiophene, aza-dibenzoselenophene and combinations thereof.

In one embodiment, R^(a) to R^(g) in Formula 1 are H. In one embodiment,Ar¹ is

In one embodiment, Ar¹ is

and Ar² and Ar³ are phenyl. In one embodiment, Ar¹ is

Ar² and Ar³ are phenyl, and L is a direct bond. In one embodiment, Ar¹and L are

and Ar² and Ar³ are phenyl.

In one preferred embodiment the donor-acceptor compound with a nitrogencontaining donor connected to the 1-position of a carbazole and triazeneas the acceptor is selected from the group consisting of

In one embodiment, Ar¹ and Ar² in Formula 1 are connected to form acarbazole moiety. In another preferred embodiment, Ar¹ and Ar² areconnected to form a carbazole moiety and the compound is selected fromthe group consisting of

In one embodiment, Ar² and Ar³ in Formula 1 are connected to form acarbazole moiety. In another preferred embodiment, Ar² and Ar³ areconnected to form a carbazole moiety and the compound is selected fromthe group consisting of

In another preferred embodiment, the compound is selected from the groupconsisting of

According to another aspect of the present disclosure, a first devicecomprising a first organic light emitting device is disclosed. The firstorganic light emitting device comprises an anode; a cathode; and anemissive layer, disposed between the anode and the cathode, wherein theemissive layer comprises a first emitting compound having a structureaccording to Formula 1:

wherein R^(a) to R^(g), R¹ and R² are independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and wherein Ar¹ to Ar³are independently substituted or unsubstituted aryl or heteroaryl andcan connect to one another to form fused ring(s) and, wherein L is adirect bond or a linker.

In one embodiment of the first device, the first emitting compound isselected from the group consisting of Compound 1 through Compound 53disclosed herein.

In one embodiment, the first device emits a luminescent radiation atroom temperature when a voltage is applied across the organic lightemitting device, wherein the luminescent radiation comprises a delayedfluorescence process.

In one embodiment of the first device, the emissive layer furthercomprises a first phosphorescent emitting material. In anotherembodiment, the emissive layer further comprises a second phosphorescentemitting material. In another embodiment, the emissive layer furthercomprises a host material.

In one embodiment of the first device, the emissive layer furthercomprises a first phosphorescent emitting material and the first deviceemits a white light at room temperature when a voltage is applied acrossthe organic light emitting device.

In another embodiment of the first device, the emissive layer furthercomprises a first phosphorescent emitting material and the first deviceemits a white light at room temperature when a voltage is applied acrossthe organic light emitting device, and the first emitting compound emitsa blue light with a peak wavelength of about 400 nm to about 500 nm.

In another embodiment of the first device, the emissive layer furthercomprises a first phosphorescent emitting material and the first deviceemits a white light at room temperature when a voltage is applied acrossthe organic light emitting device, and the first emitting compound emitsa yellow light with a peak wavelength of about 530 nm to about 580 nm.

In another embodiment of the first device, the first device comprises asecond organic light emitting device, wherein the second organic lightemitting device is stacked on the first organic light emitting device.

In one embodiment of the first device, the first device is a consumerproduct. In another embodiment of the first device, the first device isa lighting panel.

According to another aspect, a formulation comprising a compound havinga structure according to Formula 1 is also disclosed.

Synthesis of Compound 1

1-bromo-9-(4,6-diphenyl-13,5-triazin-2-yl)-9H-carbazole (0.50 g, 1.05mmol), (4-(diphenylamino)phenyl)boronic acid (0.46 g, 1.26 mmol) andPd₂(dba)₃ (0.03 g) were mixed in a 25 mL two-neck flask. The wholesystem was evacuated and purged with argon gas. The mixture wasdissolved in dry toluene (10 mL). ^(t)Bu₃P (2.51 mL, 0.05 M in toluene)and degassed K₂CO₃ (1.26 mL, 2.5 M in H₂O) were added. The mixture wasrefluxed under argon for 14 hours. After completion of the reaction, itwas cooled to room temperature and the mixture was extracted withdichloromethane. The combined organic layer was washed with brine anddried over MgSO₄ after which the solvent was removed by rotaryevaporation. The crude product was purified by column chromatography onsilica gel using hexane:dichloromethane=5:1 and then withhexane:dichloromethane:toluene=3:1:0.1 to obtained the pure product,Compound 1, (0.60 g, 90%) as a yellow solid.

Synthesis of Compound 2

1-bromo-9H-carbazole (0.50 g, 2.03 mmol), 4-(diphenylamino)phenylboronicacid (0.71 g, 2.44 mmol), and Pd₂(dba)₃ (0.06 g) were mixed in a 25 mLtwo-neck bottle. The whole system was evacuated and purged with argongas. Dry toluene (10 mL), t-Bu₃P (4.88 mL of 0.05 M in toluene anddegassed K₂CO₃ (3.66 mL, 2.5 M in H₂O) were added. The system wasrefluxed for 14 hours under an inert atmosphere. Upon completion of thereaction, the mixture was cooled to room temperature and then extractedwith ethyl ether. The combined organic layer was washed with brine,dried with MgSO₄ and finally the solvent was removed by rotaryevaporation. The crude product was purified by column chromatography onsilica gel using hexane:dichloromethane=3:1 as the eluent to obtain thedesired product, 4-(9H-carbazol-1-yl)-N,N-diphenylaniline, (0.75 g, 90%)as a white solid.

4-(9H-carbazol-1-yl)-N,N-diphenylaniline (0.50 g, 1.22 mmol),2-(4-bromophenyl)-4,6-diphenyl-1,3,5-triazine (0.57 g, 1.46 mmo),Pd₂(dba)₃ (0.03 g), and NaO^(t)Bu (0.15 g, 1.58 mmol) were mixed in a 50mL two neck round bottom flask and the system was evacuated then purgedwith argon gas. The mixture was dissolved in dry toluene (20 mL).^(t)Bu₃P (2.44 mL, 0.05 M in toluene) was added and the mixture wasrefluxed under argon for 4 hour. After completion of the reaction, itwas cooled to room temperature, the salts were filtered. After removalof the solvent by the rotary evaporation, about 10 mL of dichloromethanewas added to the crude product and heated to dissolve of the compound.Hexane was added for crystallization to take place. The solid wasfiltered and washed with hexane to afford the product, Compound 2, (0.71g, 81%) as a yellow green solid.

Synthesis of Compound 3

1-bromo-9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9H-carbazole (0.50 g, 1.05mmol),9-phenyl-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9H-carbazole(0.46 g, 1.26 mmol), and Pd₂(dba)₃ (0.03 g) were mixed in a 25 mLtwo-neck flask, evacuated and then recharged with argon. The mixture wasdissolved in dry toluene (10 mL) and then ^(t)Bu₃P (2.51 mL, 0.05 M intoluene, 12 mmol) and degassed K₂CO₃ (1.26 mL, 2.5 M in H₂O) were added.The mixture was refluxed under argon for 14 hours. Upon completion ofthe reaction, the mixture was cooled to room temperature and extractedwith dichloromethane. The combined organic layer was wash with brine,dried over MgSO₄ and the solvent was removed by rotary evaporation. Thecrude product was purified by column chromatography on silica gel usinghexane:dichloromethane=5:1, and then changed withhexane:dichloromethane:toluene=3:1:0.1 to obtained pure product,Compound 3, (0.60 g, 90%) as a yellow solid.

Synthesis of Compound 5

A solution containing9-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole(0.65 g, 1.8 mmol), Pd(PPh₃)₄ (0.09 g, 0.08 mmol), ^(t)Bu₃P (3.2 mL of0.05 M in toluene),1-bromo-9-(4,6-diphenyl-1,3,5-triazin-2-yl)-9H-carbazole (0.76 mg, 1.6mmol) and Na₂CO₃ (2.9 mL, 2M in H₂O) in toluene (30 mL) was refluxedwith vigorous stirring for 24 hours under an argon atmosphere. Themixture was poured into water and extracted with DCM. The organicextracts were washed with brine and dried over MgSO₄. The solvent wasremoved by rotary evaporation, and washed with hot DCM to afford thepure product, Compound 5, (0.45 g, 39%).

Table 1 below summarizes the photoluminescence (PL), photoluminescencequantum yield PLQY and solvatochromism data of Compounds 1 and 2. It canbe seen that in thin films (5% of emitter by weight in PMMA, mCBP or mCPas host), PLQY's in the range of 50% were obtained. Significant redshift in PL was observed as the solvent polarity increased, indicatingthe charge transfer origin of the luminescence.

TABLE 1 PL, PLQY and solvatochromism of Compound 1 and 2. Em_(max) PLQYCompound Host (nm) (%) Solution Em_(max) (nm) Compound 1 PMMA 509 57hexane 504 toluene 530 chloroform 572 Compound 2 PMMA 498 47 3- 490methylpentane mCBP 496 55 toluene 520 mCP 499 57 2-methylTHF 552

DEVICE EXAMPLES

In the OLED experiment, all device examples were fabricated by highvacuum (<10⁷ Torr) thermal evaporation. The anode electrode is ˜800 Å ofindium tin oxide (ITO). The cathode consisted of 10 Å of LiF followed by1,000 Å of Al. All devices were encapsulated with a glass lid sealedwith an epoxy resin in a nitrogen glove box (<1 ppm of H₂O and O₂) and amoisture getter was incorporated inside the package.

Device Example 1

The organic stack of the Device Examples in Table 2 consists ofsequentially, from the ITO surface, 200 Å of TAPC the hole transportinglayer (HTL), 300 Å of Compound A doped with 5% of the emitter Compound 1as the emissive layer (EML) and 400 Å of TmPyPB as the ETL. DeviceExample 1 has an external quantum efficiency (EQE) of 12% at 5 cd/m² and7.7% at 1000 cd/m². The CIE is 0.249, 0.481, with an emission peak at502 nm

The photoluminescence quantum yield (PLQY) of the neat film of Compound1 was measured to be 57% in Compound 1 in PMMA film (5% by weight). Fora standard fluorescent OLED with only prompt singlet emission, the ratioof singlet excitons should be 25%. The outcoupling efficiency of abottom-emitting lambertian OLED is considered to be around 20-25%.Therefore, for a fluorescent emitter having a PLQY of 57% withoutadditional radiative channels such as delayed fluorescence, the highestEQE should not exceed 3.6% based on the statistical ratio of 25%electrically generated singlet excitons and outcoupling efficiency of25%. Thus devices containing compounds of Formula I as the emitter, suchas Compound 1, showed EQE far exceeding the theoretic limit.

Device Example 2

The organic stack of the Device Examples in Table 2 consists ofsequentially, from the ITO surface, 100 Å of LG101 (purchased from LGChem, Korea) as the hole injection layer (HIL), 300 Å of Compound B thehole transporting layer (HTL), 300 Å of mCBP doped with 6% of theemitter Compound 2 as the emissive layer (EML), 50 Å of Compound C asETL1 and 400 Å of Compound D as ETL2. Device Example 2 has an EQE of 10%at 1 cd/m² and 7.1% at 1000 cd/m². The CIE is 0.240, 0.496, with anemission peak at 510 nm. Again, the device EQE far exceeded theconventional fluorescent device efficiency limit.

The chemical structure of the compounds used in the device examples areshown below:

Combination with Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but not limit to: aphthalocyanine or porphyrin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and across-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, butnot limit to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, azulene; group consisting aromaticheterocyclic compounds such as dibenzothiophene, dibenzofuran,dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene,benzoselenophene, carbazole, indolocarbazole, pyridylindole,pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole,oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine,pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine,indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole,benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline,quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine,phenazine, phenothiazine, phenoxazine, benzofuropyridine,furodipyridine, benzothienopyridine, thienodipyridine,benzoselenophenopyridine, and selenophenodipyridine; and groupconsisting 2 to 10 cyclic structural units which are groups of the sametype or different types selected from the aromatic hydrocarbon cyclicgroup and the aromatic heterocyclic group and are bonded to each otherdirectly or via at least one of oxygen atom, nitrogen atom, sulfur atom,silicon atom, phosphorus atom, boron atom, chain structural unit and thealiphatic cyclic group. Wherein each Ar is further substituted by asubstituent selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH)or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but not limit tothe following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40;(Y¹⁰¹-Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independentlyselected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and k′+k″ is the maximum number of ligands thatmay be attached to the metal.

In one aspect, (Y¹⁰¹-Y¹⁰²) is a 2-phenylpyridine derivative. In anotheraspect, (Y¹⁰¹ Y¹⁰²) is a carbene ligand. In another aspect, Met isselected from Ir, Pt, Os, and Zn. In a further aspect, the metal complexhas a smallest oxidation potential in solution vs. Fc⁺/Fc couple lessthan about 0.6 V.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant. While the Table below categorizes host materials as preferredfor devices that emit various colors, any host material may be used withany dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

wherein Met is a metal; (Y¹⁰³-Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴are independently selected from C, N, O, P, and S; L¹⁰¹ is an anotherligand; k′ is an integer value from 1 to the maximum number of ligandsthat may be attached to the metal; and k′+k″ is the maximum number ofligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O—N) is a bidentate ligand, having metal coordinated to atoms Oand N.

In another aspect, Met is selected from Ir and Pt. In a further aspect,(Y¹⁰³-Y¹⁰⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the groupconsisting aromatic hydrocarbon cyclic compounds such as benzene,biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene,phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; groupconsisting aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran,benzothiophene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and group consisting 2 to 10 cyclic structural units which are groups ofthe same type or different types selected from the aromatic hydrocarboncyclic group and the aromatic heterocyclic group and are bonded to eachother directly or via at least one of oxygen atom, nitrogen atom, sulfuratom, silicon atom, phosphorus atom, boron atom, chain structural unitand the aliphatic cyclic group. Wherein each group is furthersubstituted by a substituent selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester,nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

In one aspect, host compound contains at least one of the followinggroups in the molecule:

wherein R¹⁰¹ to R¹⁰⁷ is independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof, when it is aryl or heteroaryl, ithas the similar definition as Ar's mentioned above. k is an integer from0 to 20 or 1 to 20; k′″ is an integer from 0 to 20. X¹⁰¹ to X¹⁰⁸ isselected from C (including CH) or N. Z¹⁰¹ and Z¹⁰² is selected fromNR¹⁰¹, O, or S.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies as compared to a similar device lacking a blocking layer.Also, a blocking layer may be used to confine emission to a desiredregion of an OLED.

In one aspect, compound used in HBL contains the same molecule or thesame functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of thefollowing groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ isan integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, compound used in ETL contains at least one of thefollowing groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen,deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy,aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, when it is aryl or heteroaryl, it has the similar definition asAr's mentioned above. Ar¹ to Ar³ has the similar definition as Ar'smentioned above. k is an integer from 1 to 20. X¹⁰¹ to X¹⁰⁸ is selectedfrom C (including CH) or N.

In another aspect, the metal complexes used in ETL contains, but notlimit to the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinatedto atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer valuefrom 1 to the maximum number of ligands that may be attached to themetal.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated,and fully deuterated versions thereof. Similarly, classes ofsubstituents such as, without limitation, alkyl, aryl, cycloalkyl,heteroaryl, etc. also encompass undeuterated, partially deuterated, andfully deuterated versions thereof.

In addition to and/or in combination with the materials disclosedherein, many hole injection materials, hole transporting materials, hostmaterials, dopant materials, exiton/hole blocking layer materials,electron transporting and electron injecting materials may be used in anOLED. Non-limiting examples of the materials that may be used in an OLEDin combination with materials disclosed herein are listed in Table Abelow. Table A lists non-limiting classes of materials, non-limitingexamples of compounds for each class, and references that disclose thematerials.

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US20040036077 Zn (N{circumflex over ( )}N) complexes

U.S. Pat. No. 6,528,187

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

What is claimed is:
 1. A compound having a structure according toFormula 1:

wherein R^(a) to R^(g), R¹ and R² are independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and wherein Ar¹ to Ar³are independently substituted or unsubstituted aryl or heteroaryl andcan connect to one another to form fused ring(s) and, wherein L is adirect bond or a linker.
 2. The compound of claim 1, wherein R^(a) toR^(g) are H.
 3. The compound of claim 1, wherein Ar¹ is


4. The compound of claim 3, wherein Ar² and Ar³ are phenyl.
 5. Thecompound of claim 4, wherein L is a direct bond.
 6. The compound ofclaim 1, wherein Ar¹ and L are

and Ar² and Ar³ are phenyl.
 7. The compound of claim 1, wherein saidcompound is selected from the group consisting of


8. The compound of claim 1, wherein Ar¹ and Ar² are connected to form acarbazole moiety.
 9. The compound of claim 8, wherein said compound isselected from the group consisting of


10. The compound of claim 1, wherein Ar² and Ar³ are connected to form acarbazole moiety.
 11. The compound of claim 10, wherein said compound isselected from the group consisting of


12. The compound of claim 1, wherein said compound is selected from thegroup consisting of


13. A first device comprising a first organic light emitting device, thefirst organic light emitting device comprising: an anode; a cathode; andan emissive layer, disposed between the anode and the cathode, whereinthe emissive layer comprises a first emitting compound having astructure according to Formula 1:

wherein R^(a) to R^(g), R¹ and R² are independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and wherein Ar¹ to Ar³are independently substituted or unsubstituted aryl or heteroaryl andcan connect to one another to form fused ring(s) and, wherein L is adirect bond or a linker.
 14. The first device of claim 13, wherein thefirst emitting compound is selected from the group consisting of


15. The first device of claim 13, wherein the first device emits aluminescent radiation at room temperature when a voltage is appliedacross the organic light emitting device; wherein the luminescentradiation comprises a delayed fluorescence process.
 16. The first deviceof claim 13, wherein the emissive layer further comprises a firstphosphorescent emitting material.
 17. The first device of claim 16,wherein the emissive layer further comprises a second phosphorescentemitting material.
 18. The first device of claim 13, wherein theemissive layer further comprises a host material.
 19. The first deviceof claim 16, wherein the first device emits a white light at roomtemperature when a voltage is applied across the organic light emittingdevice.
 20. A formulation comprising a compound having a structureaccording to Formula 1:

wherein R^(a) to R^(g), R¹ and R² are independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and wherein Ar¹ to Ar³are independently substituted or unsubstituted aryl or heteroaryl andcan connect to one another to form fused ring(s) and, wherein L is adirect bond or a linker.